Oscillation generator



Jan. 17,1939. 4 F. H SCHEER 2,144,511

OSCILLATION GENERATOR 7 Filed Nov. 13, 1955 WITNESSES: INVENTOR 8W. Frederick HSqheeK Patented Jan. 17, 1939 UNITED STATES- BATENT OFFICE OSCILLATION GENERATOR.

Application November 13, 1,935, SerialNo. 49,512

5 Claims,

Elly-invention" relates to oscillation generators and-more particularly 'to one of the dynatron type.

It is'an objectofmy invention to provide such anoscillator; the frequency of which shall remain substantially-unaffected. by changes in effective load resistance.

Another-object of my invention is to provide a generator of the above type wherein the changes-necessary to render itunaffected by variations in eiiective load resistance are very slight.

An oscillation-generator of the dynatron type relies upon the presence of" a negative resistance characteristic for its operation. Primary electrons from the filament or cathode are caused to bombard the plate of the tube andliberate therefrom secondary electrons; that-a higher positive potential is'impressed upon the'grid' ofthe tube than that impressed on the plate, secondary electrons emitted from the plate as a result of primary bombardment, are attracted-to the grid electrode and produce current flow-in the grid circuit. It is apparent from the abovethat whatever change, the plate current may undergo by reason of oscillations generated in the plate circuit, the grid circuit will undergo corresponding changes since electrons leaving the plate are attracted by the grid and add to its current. A circuit capable of being tuned to the same frequency as the tankcircuit, which is normally'located in the plate circuit of the oscillator and placed in thegrld circuit, will'have oscillationsinduced in it.

In accordance with the teachings of my 'invention, I propose toinsert such a tunable circuit in the grid circuit of a dynatron oscillator, and couple the load circuit to this tunable circuit, instead of the plate circuit, as is the customary practice, and then neutralize the oscillator to prevent load variations from. altering the frequency characteristic of the circuit.

It is well known in the prior art that variations in load may cause such reactions upon the oscillation generator feeding the load as to produce a change in its frequency of oscillation. This holds good also for oscillators of the dynatron type where the load is coupled to the tank circuit, which is the circuit that'determines the frequency of the generator.

By inserting a tunable circuit in the grid circuit of the oscillator, as proposed above, and then neutralizing the oscillation generator in a manner which will be hereinafter described, the load circuit is effectively isolated from the frequency determining or tank circuit, and as a result, var- By reason of'the fact iations in load exert practically no influence upon the frequency of the oscillator.

In Fig. 1 and Fig. 2 of the accompanying drawingyI have illustrated two embodiments of my invention. Ineach of these embodiments I series with a portion of the power supply source It; the negative end of which is grounded. In the grid circuit'I have interposed a resonant circuit comprising an inductor I5 and a shunting condenser ll tunable to the frequency of the tank circuit. The grid 5 is connected'to one terminal of this tunable circuit, whereas the extreme posi tive terminal of the powersupply source IBfeeding the grid is connected to the midpoint or an intermediate point on the coil l 5. For simplicity of illustration as well as economy in practical operatiojn, the same source of supply is shown for delivering energy to both the grid and the anode, although separate sources may as well be employed: The filament is grounded to complete the grid and plate circuits of the oscillator.

Neutralization of the oscillator in this embodiment of my invention isv obtained by connecting a'small neutralizing condenser l9 between the free end of the grid tunable circuit and the plate I of the electron discharge device, thus completing a bridge circuit wherein each section of the grid coil l5 constitutes an arm of a bridge and the neutralizing condenser l9 and the grid plate capacity comprise the other two arms of the bridge circuit.

The load which is to be fed from the oscillator is coupled to the grid coil I5 and in view of the fact that the grid coil comprises two arms of a balancing bridge network, any variations in load will be neutralized in the bridge circuit and. will not be communicated to the tank circuit. Since the tank circuit determines the frequency of the generator, it follows that the frequency thereof will not be afiected as a result of any changes occurring in the effective load resistance.

In the second embodiment of my invention, as illustrated in the circuit of Fig. 2, the tank circuit comprising coil 2! and condenser 23 is made a part of the bridge network or neutralizing circuit instead of the tunable grid circuit 25-21,

' point thereon beingf capacitively connected to i said grid, a source of potential supply connected Thus, the tuned circuit is connected in the grid circuit with the, grid at one end and the other end connected to the power supply source.

The tank circuit on the other hand, is connected one end directly to the plate of the tube and a midpoint tap or an intermediate point to the power'supply source for the anode; The free end of the tankcircuit is then connected by means of a small neutralizing condenser 29 to the grid 5 of the electron discharge device, thus completing the bridge network which now comprises the tank coil 2! as constituting two arms of the bridge and the neutralizing condenser 29 and grid plate capacity as constituting the other two arms.

Regardless of which modification or embodiment is relied upon, variations in load circuit cannot be transmitted to the tank circuit or frequency determining portion of the oscillator, and consequently, the frequency'of the oscillator will remain constant insofar as load changes may be involved,

While I have described my invention in great 7 detail, various modifications may be made therein without departing from the scope of my invention, and I desire that only such limitations, shall be imposed thereon as are indicatedin the appended claims. a

I claim as my invention: V

1. ,In combination, an electron discharge device comprising cathode, ancde'and grid electrodes, a

circuit connecting said grid and said cathode;

said circuit including a source of positive potential' for said grid a second circuit connecting said anode and cathode, said second circuit being cannected to an intermediate point on and including a portion of said source of potential for said anode and an pedance element t'unable'to a desired frequency, said impedance element be-V,

ing connected to an intermediate point on said source of potential, means for coupling said element directly to one of said positively biased electrodes and capacitively to said other positively biased electrode in opposing relation with respect, to said intermediate point.

2. In combination, an electron discharge device comprising a cathode, and anode and grid electrodes, an impedance, one point of 'which isconductively connected to said anode, another in circuit between said cathode and an intermediate'point on'saidimpedance, andwa second impedance in series with a source ofpotential supply of higher value than said first potential supply, connected in circuit between said cathode and said grid electrode.

3 In combination, an oscillation generator of the dynatron type comprising an electron discharge device having cathode, grid and anode electrodes, a circuit interconnecting said cathode with saidgrid and another'circuit interconnect-' ing said cathode'and anode electrodes, said cir-' cuits being substantially free from regenerative coupling, means for'maintaining said grid at a positivepotential higher than said anode with respect to said cathode and means in said anode 'circuitffor determining the frequency of said said cathode and each of said pair, the potential between-said cathode and the nearer of said pair being higher in a positive sense than the potential between the cathode and said electrode farther therefrom,'an impedance having one portion thereof conductively connected to one of said pair and its associated source, and having another portion thereof capacitatively connected to the other of said pair, and a tuned circuit conneoted between said cathode and one of said pair.

5. In combinationyan oscillation generator of the dynatron type comprising an electron discharge device having cathode, grid and anode electrodes a circuit interconnecting said cathode with said grid and another circuit interconnect ing said cathode withsaid anode electrodes, said circuits being substantially free .irom regenerative coupling, means for'main'taining said grid at' a positive potential higherthan said anode with respect to said. cathode and means in said anode circuit for determining the frequency of said oscillation generator, said means comprising a resonant tank circuit, and a load circuit coupled to derive energy from said grid circuit, and a capacity interconnecting said grid and plate circuits for neutralizing the efiect of variations in said load circuit. V FREDERICK I-I. SCHEER. 

